This invention relates generally to methods and devices used with water systems. More particularly, it relates to a method and apparatus for exposing water which flows through a water system to an ion generator whereby ions which are generated are fed into the water flow to prevent fouling of the water system by algae, nuisance invertebrates, microorganisms, and inorganic salts.
It has long been known that algae, nuisance invertebrates, microorganisms, and inorganic salts may foul water systems and lead to very significant water system inefficiencies. These inefficiencies result in increased energy consumption and increased maintenance demands which, in turn, increase overall operational and maintenance costs by several orders of magnitude. Ion generators have been employed in previous attempts to control algae, nuisance invertebrates, and microorganisms. Such ion generators are based on well-known principles of electrochemical reactions, one of which is referred to as electrolysis. Electrolysis is an electrochemical process by which electrical energy is used to promote chemical reactions that occur on the surface of functionally cooperating electrodes. One electrode, called the anode, involves the oxidation process where chemical species lose electrons. A second electrode, called the cathode, involves the reduction process where electrons are gained. In water, for example, oxygen is generated at the anode and hydrogen is generated at the cathode. The generation of hydrogen and oxygen in fresh water by the process of electrolysis will be weak due to the low electrical conductivity of the water. The oxygen generated aids in the prevention of the deposit of inorganic salts on the electrodes. The function of an ion generator is also to produce metal ions, typically copper ions or silver ions. Metal ion production is accomplished by use of an electrically charged metal anode which comprises atoms of the metal ions which are to be generated. It is the purpose of the ion generator to feed the metal ions out of the generator before they can be deposited on a cathode. Such depositing completely defeats the purpose of the ion generator as it is intended to be used in the application described here. The metal ions and oxygen, both of which are produced by the ion generator in the present application, are feed into the water stream of the water system to prevent fouling of the system by algae, nuisance invertebrates, microorganisms, and inorganic salts.
Copper, in its dissolved form, is one anthropogenic heavy metal that, although essential to biological functions in trace amounts, can be toxic at higher concentrations. The toxicity of copper to aquatic organisms is well established although the exact mechanism is not well defined. Copper toxicity is related to the form and, in general, copper must be in an ionic form in order for it to be toxic to invertebrates, microorganisms and algae. The eradication of microorganisms with copper ions is attributed to positively charged ions which are both surface active and microbiocidal. These ions attach themselves to the negatively charged bacterial cell wall of the microorganism and destroy cell wall permeability. This action, coupled with protein denaturation, induces cell lysis and eventual death. The in-water residence time for the biologically toxic portion of ionized copper may well be on the order of hours. One advantage to the use of copper ionization is that eradication efficacy is wholly unaffected by water temperature. Chlorine, a commonly used antifouling chemical, is somewhat temperature dependent. Furthermore, the copper ions actually kill the microorganisms, and other microorganism promoting bacteria and protozoa, rather than merely suppress them, as in the case of chlorine. This minimizes the possibility of later recolonization. Other advantages of copper ionization compared to other eradication techniques include relatively low cost, straight forward installation, easy maintenance, and the presence of residual disinfectant throughout the system.
A copper ion generator is, by way of specific example, an effective method for controlling legionella which is likely to be present in most water systems. Legionella is predominantly present in water cooling systems in microbial biofilms which become attached to surfaces submerged in the aquatic environment. These biofilms are typically found on the surfaces of pipes and stagnant areas of the water cooling system. Many components of most any man-made water system can be considered to be an amplifier for the organism (i.e., the organism can find a niche where it can grow to higher levels, or be amplified) or a disseminator of the organism. Examples of man-made amplifiers include cooling towers and evaporative condensers, humidifiers, potable water heaters and holding tanks, and conduits containing stagnant water. Showerheads, faucet aerators, and whirlpool baths may serve as amplifiers as well as disseminators. Human infection from exposure to legionella, or legionosis, can result in a pneumonia illness that is commonly referred to as Legionnaire""s disease, namesake of the famous 1976 outbreak in Philadelphia. Since the Philadelphia outbreak, about 1,400 cases are officially reported to the Center for Disease Control annually.
Other bacteria and protozoa can also colonize water cooling system surfaces and some have been shown to promote legionella replication. Amoebae and other ciliated protozoa are natural hosts for legionella. Legionella multiply intracellularly within amoebae trophozoites. Logionella pneumophila is known to infect five different genera of amoebae, most notably Hartmanella vermiformis and Acanthamoeba. Legionella can also multiply within the ciliated protozoa, Tetrahymena. Bacterial species that appear to provide legionella with growth promoting factors include Pseudomonas, Acinetobactor, Flavobacterium, and Alcaligenes. Copper ions are an effective method of control for each of these bacteria and protozoa.
The controlled release of copper ions has also been known to serve as an effective attachment and growth control for such marine organisms as algae, mussels, oysters and barnacles. Copper ions can eliminate and control algae, for example, by inhibiting photosynthesis which leads to its demise. And copper ions have been shown to be more lethal to the zebra mussel than other metal ions. For effective zebra mussel control in freshwater, for example, copper ion concentrations of eight parts per billion are estimated to be required, which is a level well below that recommended by the Environmental Protection Agency for freshwater aquatic protection.
The design of ion generators for salt water can generally be considered trivial. Due the high electrical conductivity of salt water, factors such as electrode spacing are not important. In fact, electrodes used in salt water application can be spaced many tens of centimeters apart without any consequential effect on system operation. Problems such as xe2x80x9cbridgingxe2x80x9d of inorganic salts between the anode and the cathode, which leads to electrical shorting and conductivity stratification, are not a factor. The design and operation of copper ion generators in fresh water systems is consequentially different than the design employed in salt water systems. Simply put, the design and operational differences of salt water and fresh water copper ion generation systems are fundamentally related to the large differences, of several orders of magnitude, in electrical conductivity. Because of those differences, the present art employed in the design and operation of commercial copper ion generators for fresh water cooling systems has significant operational problems. In the experience of these inventors, users of present copper ion generators in industrial cooling water systems have reported problems such as bridging which leads to electrical shorting, electrical conductivity stratification which results in uneven electrode erosion, and plating of copper on the cathode.
Bridging, as previously described, occurs because of the necessity of placing the anode and cathode in close proximity to one another in fresh water systems. One way of dealing with this problem is to periodically reverse polarity of the electrodes. This solution, however, introduces system inefficiencies due to the fact that polarity reversal renders the system non-functional for the period of time that polarity is reversed. Uneven electrode erosion due to electrical conductivity stratification occurs for the reason that nonuniform water flow occurs between electrodes. In present designs, the velocity of the water which flows between the electrodes is not generally constant over the electrode face. This leads to stratification of inorganic materials in the water which, in turn, produces electrical conductivity stratification. Finally, plating of the metal anode material on the cathode, as previously mentioned, completely defeats the purpose of the ion generator in the present application. When plating occurs, the metal ions are deposited on the cathode rather than being introduced into flow stream that is to be treated. In the experience of these inventors, each of these problems is related to water flow and to electrode spacing, which is required to be very close in fresh water systems when compared to systems designed for use in salt water. The spacing of the electrodes in close proximity to each other in fresh water systems is required if power system expectations are to be within reason, on the order of a few hundred watts. The system simply will not be economical if maximum power requirements exceed several kilowatts.
It is, therefore, a principal object of this invention to provide a new, useful, and uncomplicated method and apparatus for exposing the water flow within a water system to an ion generation device wherein water velocity is increased between the electrodes of the ion generator. It is another object of this invention to provide such a method and apparatus where a tangential inlet is provided to create a high velocity vortex flow within the system in the vicinity of the ion generator electrodes. It is yet another object to provide such a method and apparatus which avoids xe2x80x9cdead zones,xe2x80x9d or areas where water velocities in the vicinity of the ion generator electrodes are low. It is still another object of the present invention to provide such a method and apparatus in which the aspect ratio (i.e., the ratio between the system inlet and the system containment tank diameter) is defined to lock on to a water flow velocity range which must be maintained for proper system operation and in which the residence time of flow within the system is similarly defined and maintained. It is still another object to provide such a method and apparatus in which a non-electrical conducting head is used to mount the electrodes of the ion generator and where a plurality of cooperatively alternating anodes and cathodes may be used. It is yet another object of the present invention to provide such a method and apparatus in which an automatic discharge valve is provided to control the system water level within the ion generator thereby maintaining a minimum vertical velocity, within the system. It is still another object to provide a self-cleaning elliptical or conical base to the flow tank. It is yet another object to provide such a method and apparatus wherein a sight glass is utilized to allow for visual inspection of anode wastage. It is still another object to provide such a method and apparatus wherein performance is optimized while manufacturing costs are not increased significantly.
The present invention has obtained these objects. It overcomes the aforementioned problems and disadvantages by providing a method and apparatus in which water flowing through a water system is vigorously and turbulently exposed to a plurality of electrodes of an ion generator whereby ions which are generated are fed into the water flow to prevent fouling of the water system by algae, nuisance invertebrates, microorganisms, and inorganic salts. The present invention accomplishes this by providing an ion generator having a self-contained tank through which the water flows. The generally cylindrical containment tank includes a tangential inlet pipe at the uppermost portion of the tank. An elliptical tank base includes an outlet pipe in combination with a tank clean out device at the lowermost portion of the tank. An aspect ratio, inlet pipe diameter versus containment tank diameter, is defined to achieve optimum ionization. A tank cover is provided which serves as the non-electrical conducting head for a plurality of electrodes which extend downwardly from the underside of the cover. When the tank cover is in place in its normal operating position, the electrodes are suspended from the tank cover within the containment tank. The electrodes are functionally configured, both in size and placement, to maximize water flow between them. The rate of water flow within the containment tank is defined such that residence time of flow within the tank likewise optimizes water ionization. A sight glass is provided within the containment tank to allow for visualization and monitoring of the container contents, and in particular anode wastage or wear, during operation. The foregoing and other features of the method and apparatus of the present invention will be apparent from the detailed description which follows.